Use OBS to capture your screen and manipulate it however you want and then use its virtual camera feature as your webcam for the meeting. If you want both your face and screen you could easily do a facecam in the corner in obs
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I second this. The OBS virtual camera is great for stuff like this. Works with any software that a webcam works with.
I think I'd recommend OBS too, but I guess this is possible with an application I wrote.

If you want to install it, it is available on Flathub here.
Not OP but this actually looks really nice! Good job mate, I will probably DL later to try it out.
Thanks. It's really intended to solve picture in picture for any application, but it looks like it does exactly was OP was requesting too.
I know this doesn't solve your immediate problem when using GNOME, but if you are desktop curious, KDE natively offers sharing a portion of the screen or even creating a whole new virtual monitor with its own resolution, wallpaper etc that you can share.
So my typical workflow is to have it create a 1080p virtual monitor above my real monitors, and share that, since sharing a full 4k monitor makes it hard for people to read. Then I can show whatever I want on that monitor without worrying about exposing something from my main monitors.
That's very cool. Hopefully GNOME will steal this idea one day.
Man the more I learn about KDE, the more I love it.
Maybe this can help. Basically you're looking to split your screen into virtual screens.
Don't know if this will work on the fly though.
OH - check if your monitor supports PBP - Picture by Picture. Some Ultra-wides have this functionality, and you can run two cables from the computer to the monitor (assuming you have 2 video outs) and the monitor itself will show up in the OS as two smaller monitors instead of one big one. If your monitor has this feature and you have two video outputs, it sounds like it would do exactly what you want.
Also, to add to what others have said, OBS will very likely do almost everything you are wanting, but if you want to be able to have your "webcam" and "screenshare" separate I have a silly solution for you... Use OBS to get the half of the monitor you want to share piped into it, but instead of using the virtual camera, pare down everything in OBS you don't need to see so it is basically just the preview and then in the meeting software share the OBS window. You can still use your normal webcam setup for your face, and a "screen share" option for your screen share, not limited to any windows (even though the thing thinks it is limited to OBS, but OBS sees the other windows you need and just takes up a little bit of border area). It's silly, and it isn't perfect, but it gets you 90% of the way there.
I have funky screen configurations too. What I've done is setup a headless screen that I view over VNC on a tablet and share that. On Wayland wayvnc can do this.
How exactly does that work?
On Sway:
This goes in Sway's config...
output HEADLESS-1 {
pos 5120,0
mode 1920x1080@20Hz
bg ~/tausta_kuva fill
}
And this alias starts wayvnc.
alias RuutuVNC='swaymsg create_output && nohup wayvnc 0.0.0.0 5900 >/dev/null &'
After that, connect the VNC client on the tablet to port 5900 on the machine and sail the mouse cursor over to it when selecting the screen to share.
There must have been a config for wayvnc somewhere, but I can't find it. I don't need to use this anymore after switching from a dual portrait setup to a dual LG DualUp setup, so that my screens are now pretty much square and the right way around. On the dual portrait setup, my screenshare would show up sideways in landscape :D
Thabks a lot!
Does your screen not have a built-in settings menu where you can turn off the stretching?
I always share a tab or window because then screen ratio becomes irrelevant, or am I missing something special about your setup?
The problem is that I need to switch workspaces rapidly as part of the share: terminal → browser → IDE → browser → IDE → terminal, etc. I can't be constantly going back and toggling which window I'm sharing.
[I've now edited the initial question to reflect this]
Ah, in that case I'd try OBS. You can capture and "share" half your screen with OBS if your meeting software works with the OBS camera output. You add your camera as a source in OBS if you also want to be on the screen while sharing.
I'd select one window and just scale that down.
That won't do in my case 'cause I need to share multiple windows throughout the session as I switch between my terminal/IDE/browser etc.
[I've now edited the initial question to reflect this]